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Fostex X-28 start and stop very quickly

Discussion in 'Vintage Analog Gear' started by bcwilliamson, Jul 22, 2010.

  1. bcwilliamson

    bcwilliamson Active Member

    Oct 20, 2009
    Memphis, TN
    Home Page:
    Sorry if this is the wrong forum.


    I just acquired a Fostex X-28 four track cassette recorder for cheap to record demos on while I search for a proper recording set-up.

    Everything works fine, it turns on, the inputs work, it plays back, records, and so on.

    But, and I need help with this, often when I put a cassette in for the first time, and press play, it will start and stop very quickly. This may repeat 2-3 times, with the cassette playing for longer before stopping each time. And then it seems to get used to the tape and it plays fine. Now this is not a huge issue for recording, but it is annoying and will create issues when recording with my band.

    Does anyone know what the problem is? The motor, the heads, the drive belt? I'm not at all technical so I won't be able to repair it, but I'd like to know where I should be looking. And if there is a fixable problem, would an average electrical repairs shop be able to help? It'd be nice to know that I can take it to some place near me and have it fixed inexpensively.

    Many thanks.
  2. dvdhawk

    dvdhawk Moderator Resource Member

    Dec 18, 2008
    Western Pennsylvania, USA

    First, as a matter of good practice when you get this baby up and running - you should FF and Rew a new tape from end to end to loosen the tape up before you use it. It will pull smoother through the tape mechanism. And that's also good if you did a lot of stopping and starting during the session. The tape bunches up and can pack unevenly on the cassette hubs as you start/stop/rewind - you'll see why in a minute.

    Secondly, I'd guess all the belts, tires, and pinch-roller should be replaced or at least chemically reconditioned on a unit of that age. My guess is the take-up reel isn't pulling out the slack on the first attempts*, and a pressure sensing switch detects the lack of tension and shuts off to prevent the tape from being eaten (wrapped around the capstan). This is usually caused by a belt or tire that has lost its ability to grip. Rubber dries and hardens with a bit of glaze, and/or sometimes excess lubricants from the rest of the mechanism will settle on the rubber parts. You need a certain amount of friction in all the right places (rubber parts) and the lubricants to stay where they belong (on gears and hubs).

    Without being a technician you can probably see whether the take-up reel of the tape (the one on the right that the tape should be travelling to) is sluggish when you hit "play". Does it spin right away? Does it slip at first, then try to catch up?


    The capstan is what actually controls the speed of the tape as it travels over the heads. It should be nice and clean and free of any brown residue that might have rubbed off any cheap tapes from the past.

    The pinch-roller pinches against the capstan with the tape pressed between them and provides enough grip to pull the tape smoothly across the heads.

    The take-up is just there to take up the slack after the tape passes through the pinch-roller and capstan. It is driven by an idler tire which doesn't pull the tape, it just takes up slack. If the take-up slips and the tape keeps coming there is usually a micro-switch somewhere that disengages the motor and capstan. Otherwise tape would keep coming with nowhere to go (but after a brief log-jam it would get mangled in the still moving pinch-roller and capstan).

    *Idlers slipping will often cause the problem you're describing. I don't know about your specific machine, but there's almost always an idler tire on the machine either hidden under a metal plate on the front/top of the tape well - or inside the machine. It flip flops back and forth between the forward take up side and the rewind side and provides the power to pull the tape whichever way it needs to go FF/REW. In Play mode, the take-up mechanism is designed to slip a little bit as needed (think about how the diameter would change depending on whether the tape is at the beginnng vs. the end).

    Belts are dirt cheap if you can find them. I've still got a couple vendors like MCM that sell belts. I'm sure there are others. You should physically measure the existing belts and subtract about 10% from the diameter to allow for the amount they have probably stretched over time. Try to get the other dimensions as close as possible (belt thickness and shape).

    Idler tiers should be a very specific diameter. There isn't much margin for error there, it has to be the right size or bad things can happen.

    Pinch-rollers should be an exact match and it can much harder to find unless they're a common size. The good news is, unless it's got a big crease in it from being improperly stored pressed against the capstan, you should be able to go a long time before it needs replaced. But it may need chemically revitalized from time to time.

    DO NOT CLEAN RUBBER PARTS WITH ALCOHOL - sorry for shouting, force of habit ...
    Alcohol dries rubber and will make it hard, inflexible (in other words useless).
    If you want to use alcohol to clean the heads, that's your business - just don't use it on the rubber.

    If replacing belts, idler tires, and pinch roller isn't always necessary. If they're not too far gone, a good Rubber Cleaner is always worth a shot. The only word of warning there is, PATIENCE. Don't chemically treat the pinch roller and put a tape in 5 seconds later to see if it worked. The chemical has to have an hour or two to dry, otherwise the somewhat caustic chemical will make the tape tacky and you'll ruin the tape and maybe a whole lot more as it sticks to the pinch roller and gets tangled around it.

    While you're at it, demagnetize the heads and you're ready to go!

    If you don't feel comfortable taking on a project like this, I like your chances of finding somebody who would be willing to do it for you at a fair price in a great music town like Memphis.

    Good luck, I hope that helps.
  3. bcwilliamson

    bcwilliamson Active Member

    Oct 20, 2009
    Memphis, TN
    Home Page:
    Oh, I hadn't been notified that I'd received a reply to my thread, so I didn't notice your response until yesterday. I'm overawed by it, thank you so much for your detailed advice- I've put it into action and I'm receiving far better results than before. Thank you!

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